WO2023111416A1

WO2023111416A1 - Method for monitoring the state of health of a battery with explosive cells and device implementing this method

Info

Publication number: WO2023111416A1
Application number: PCT/FR2022/052211
Authority: WO
Inventors: Romain SCHMITTER
Original assignee: Safran Electrical & Power
Priority date: 2021-12-14
Filing date: 2022-12-01
Publication date: 2023-06-22
Also published as: FR3130387A1; FR3130387B1

Abstract

One aspect of the invention relates to a method (100) for monitoring the state of health of a battery with explosive cells comprising a plurality of internal components that are distributed throughout a plurality of regions (region 1, region 2), each region of the battery comprising at least one explosive cell, each internal component being associated with a means for checking the coherence of the internal component, the method comprising at least: - a first check (110) for checking the coherence of the data of a first internal component in a region of the battery; - a second check (110) for checking the coherence of the data of a second internal component in the same region of the battery, the first and second checks being spaced apart by a predefined period of time (X). Another aspect of the invention relates to a device for monitoring the state of health of a battery with explosive cells, the device comprising a member for monitoring the battery, this member being located outside the cells of the battery and implementing the method according to the present invention.

Description

DESCRIPTION

Method for monitoring the state of health of a battery with explosive cells and device implementing this method

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for monitoring the state of health of a battery with explosive cells such as a Li-ion or post Li-ion battery. It also relates to a device for monitoring the state of health of a battery implementing this method.

The invention finds applications in the field of batteries with explosive cells and, in particular, in the field of electric batteries intended for aeronautics.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Lithium-ion, or Li-ion, batteries are batteries with explosive cells, that is to say the cells of which can thermally runaway and explode. Indeed, a Li-ion battery comprises several elements, called cells, the number of which varies according in particular to the power of the battery. Each cell of a Lithium-Ion battery includes a positive electrode (anode), a negative electrode (cathode) and an ion-conducting electrolyte allowing Lithium ions to migrate from the cathode to the anode during battery charging , and from the anode to the cathode, during its discharge.

[0004] By the very fact of their design, lithium-ion batteries can be dangerous because their cells are liable to explode as a result of thermal runaway, causing great damage. Indeed, thermal runaway can result in the generation of gases, some of which are toxic, flames, smoke, and even violent explosions. There are many causes that can cause thermal runaway, such as overheating, electrical abuse, mechanical abuse, thermal abuse, vibration, etc. While some of these causes can be avoided by controlling the handling and storage of Li-ion batteries, other causes unfortunately cannot be controlled, such as manufacturing defects. Indeed, a defect, like an impurity that gets in in a cell of the Li-ion battery, at the time of manufacture of said battery, can generate a resistance within the cell, at the origin of a thermal runaway.

[0005] Given the design of these Li-ion batteries, the higher the power of a battery, the higher the risk of explosion and the greater the damage when the battery releases the stored energy in an uncontrolled manner. .

[0006] In the field of aeronautics, the batteries must be able to be installed on electric aircraft or hybrid aircraft. The batteries must therefore be high-power batteries. However, if a high-power battery experiences thermal runaway, particularly when the aircraft is in flight, the consequences can be dramatic. Indeed, even if most Li-ion batteries incorporate means to contain thermal runaway, thermal runaway cannot be contained for very long. It is therefore important that personnel in the cockpit of the aircraft can be warned of a risk of thermal runaway so that they can abort the flight and plan a safe landing as quickly as possible.

[0007] Solutions have been proposed for monitoring thermal runaway. Several of these solutions have been described in the document “A survey of methods for monitoring and detecting thermal runaway of lithium-ion batteries” by Z. Liao, S. Zhang, K. Li, G. Zhang and T. G. Habetler, Journal of Power Sources, Elsevier, 20/07/2019. Some of these solutions are based on algorithms using the data provided by the sensors present in the battery, such as voltage sensors, temperature sensors and current sensors. The disadvantage of this type of solution is that it must be ensured that the thermal runaway actually takes place in order to avoid false positives; for this, it is necessary to know and characterize the thermal runaway. Moreover, as there are an infinite number of thermal runaway scenarios, the algorithms generally integrate all these scenarios, which leads to over-instrumenting the battery and increasing its mass and cost.

[0008] Other thermal runaway monitoring solutions have been proposed, based on the addition of dedicated sensors such as pressure sensors, gas, sound, etc. The disadvantage of this type of solution is that the addition of sensors induces an addition of mass (due not only to the mass of the sensors but also to the volume occupied by the sensors which implies a larger battery box) and cost related to the use of these sensors. In addition, this type of sensor requires an electronic card to analyze the signal returned by the sensors, which further increases the mass and the cost of this solution.

[0009]There is therefore a real need for a means making it possible to monitor the state of health of a Li-ion battery in order to detect potential thermal runaway within the battery, this means having to be simple to implement and easily embarked on board an aircraft (that is to say with little or no added mass). Such a means is all the more necessary since an aeronautical safety standard requires the onboarding of at least two dissimilar means to detect thermal runaway on board an aircraft.

SUMMARY OF THE INVENTION

[0010] To respond to the problems mentioned above of complexity, mass and cost of the means for monitoring thermal runaway in a Li-ion battery, the applicant proposes a method for monitoring the state of health of an explosive cell battery using internal battery components. In this process, it is considered that the absence of data provided by defective internal components constitutes a source of information on the state of health of the cells of the battery.

According to a first aspect, the invention relates to a method for monitoring the state of health of a battery with explosive cells comprising a plurality of internal components distributed in a plurality of zones, each zone of the battery comprising at least an explosive cell, each internal component being associated with a means for checking the consistency of said internal component, the method comprising at least: a first data consistency check of a first internal component of a zone of the battery, and a second data consistency check of a second internal component of the same area of the battery, the first and second checks being spaced apart by at most a predefined time interval, thermal runaway being detected when first non-coherent data is detected during the first consistency check and second non-coherent data is detected during the second consistency check.

[0012] This method makes it possible to monitor the state of health of the battery by using only the components already present in said battery, which makes it possible not to increase the mass of the battery, nor its cost. The method is also relatively simple to implement insofar as, outside the time window considered, it is independent of any thermal runaway scenario and any characterization of the thermal runaway signature.

This method can be implemented for all kinds of high power batteries whose cells are explosive. It can of course be implemented on Li-ion batteries or on batteries whose chemistry is still under development, called post Li-ion batteries.

In addition to the characteristics which have just been mentioned in the previous paragraph, the method for monitoring the state of health of a battery according to the invention may have one or more additional characteristics from among the following, considered individually or according to all technically possible combinations: it comprises: a plurality of first and second consistency checks, each combination of first and second consistency checks being carried out for a set of first and second internal components, of different natures; and detecting a potential thermal runaway when inconsistent first and second data is detected for a set of first and second internal components. it comprises a thermal runaway confirmation when at least a first and a second potential thermal runaway are detected, the first potential thermal runaway resulting from non-coherent data of a first set of first and second internal components of the same zone , the second potential thermal runaway resulting from non-coherent data from a second set of first and second internal components of the same zone. the internal battery components include at least one data sensor positioned within the battery cells and/or at least one data bus positioned near the battery cells. the data sensors include voltage sensors and/or temperature sensors. the time interval is of a predefined duration, varying between a few minutes and a few tens of minutes. a zone comprises a cell or a set of several cells of the battery. the number of internal components in the same zone of the battery is a predefined parameter depending on the battery, this number being at least equal to two.

According to a second aspect, the invention relates to a device for monitoring the state of health of a battery with explosive cells, characterized in that it comprises a battery management member, located outside battery cells and implementing the method as defined above.

[0016] This device has the advantage of being able to be implanted in an already existing component of the battery and, consequently, of not generating any additional mass.

[0017] Advantageously, the battery management unit comprises a unit for determining thermal runaway receiving, as input, data relating to the internal components and supplying, as output, thermal runaway information and a location of said thermal runaway. BRIEF DESCRIPTION OF FIGURES

Other advantages and characteristics of the invention will appear on reading the following description, illustrated by the figures in which:

FIG. 1 represents, in the form of a functional diagram, a general embodiment of the method for detecting a thermal runaway according to the invention;

[0020] FIG. 2 represents, in the form of a functional diagram, an example of the method according to the invention in which the internal components comprise temperature sensors, voltage sensors and data buses whose losses are processed in parallel ;

FIG. 3 represents, in schematic form, a unit for determining thermal runaway according to the invention, integrated into the battery management unit;

FIG. 4 schematically represents an example of implementation of the method of FIG. 2; And

[0023] FIG. 5 represents examples of timing diagrams in a simulation of the process with a temperature sensor and a lost data bus.

DETAILED DESCRIPTION

An exemplary embodiment of a method for monitoring the state of health of a battery with explosive cells is described in detail below, with reference to the accompanying drawings. This example illustrates the characteristics and advantages of the invention. It is however recalled that the invention is not limited to this example.

In the figures, identical elements are identified by identical references. For reasons of legibility of the figures, the size scales between the elements represented are not respected.

[0026] An example of a method 100 for monitoring the state of health of an explosive cell battery is represented according to a general embodiment in FIG. According to this method 100, the state of health of the battery is monitored by detecting the presence of a thermal runaway. It is considered that there is a risk of thermal runaway when at least two of the internal components of the battery, which are located in the same area of said battery, are considered "lost", during the same time window. An internal component is considered "lost" when the battery management device no longer receives data from this internal component. This loss of an internal component is detected by checking the consistency of the internal component. Indeed, in the event of thermal runaway, the electrical power path is generally damaged; the data of the internal component is then inconsistent; the loss of the internal component can be determined by the reception of outlying current values (for example, alternation between no current and other current values).

[0027] The loss of an internal component can be the consequence of several causes but, in the event of thermal runaway, many losses of internal components are detected in a reduced time window. Indeed, a battery with explosive cells (more simply called a battery), such as a Li-ion battery, comprises several cells, placed next to each other and connected to each other. Each cell is susceptible to thermal runaway (named TR in the figures) which generally spreads rapidly to other cells. Each cell comprises a plurality of internal components, for example sensors and/or data buses. The sensors are linked to the battery management unit via data buses, or communication buses; they thus provide the battery management unit with various data, such as voltage, current, temperature data, etc., via the data buses. A battery therefore comprises, by design, several so-called “internal” components distributed by zones in the battery, and the method of the invention takes this physical implementation of the sensors into account by defining detection zones linked to this implementation. The zones of the battery can, for example, each be formed of a single cell or, on the contrary, of a set of cells.

In the method 100 of the invention, the lost components are detected for which the management unit no longer receives data and it is checked, on the one hand, whether these components have been lost during the same time window and, on the other hand, if these lost components are positioned in the same zone of the battery. The method of the invention is based on the dynamics of thermal runaway and in particular on the fact that thermal runaway destroys several internal components as it propagates. The method thus exploits the fact that the loss of information from the internal components constitutes information in itself. More specifically, and with reference to Figure 1, the method includes steps 110 to 160 set out below.

[0030] Step 110 is a lost component detection step. This step is performed by checking whether the data of the internal component is consistent. If the data of the internal component, which the battery management unit receives, are inconsistent, that is to say if they are inconsistent or if they are non-existent, then said management unit considers that the internal component is lost. Indeed, in the event of thermal runaway, the internal component can: either be completely destroyed and, in this case, the battery management device no longer receives data from said internal component (the data is non-existent), or be partially damaged and, in this case, the battery management unit receives inconsistent data.

[0031] In step 120, the method determines whether this component has been lost for longer than a predefined time interval, also called a predefined time window. This time window, or time interval X, is defined in minutes or seconds depending, for example, on the number of cells in the battery and the size of these cells. This time window can be for example a few minutes or a few tens of minutes, depending on the battery considered and/or its integration in the aircraft. Of course, the order of magnitude of the time window may vary depending on the size of the batteries and/or their implementation. The time window makes it possible to check whether the loss of the component is potentially due to a thermal runaway or rather to a specific problem specific to this component, such as a disconnection of the component or a fault of said component. Indeed, if a component has been lost outside this time window, for example an hour earlier when the time window is a few minutes, this means that the component has suffered a one-time problem; in the event of thermal runaway, the propagation of the thermal runaway is rapid and several components are destroyed rapidly one after the other. Step 120 makes it possible to verify that the loss of the component is recent. If the loss occurred before the time window, then the process does not proceed. On the contrary, if the loss of this component is recent and occurred during the time window, then the method goes to step 130. [0032] In step 130, the method verifies whether more than Y components, lost during this time window, are located in the same zone of the battery. The threshold number Y of lost components is a predefined number, determined as a function in particular of the number of internal components and of the number of cells of the battery. If this is the case, that is to say if more than Y lost components come from the same zone, then the method considers, in step 140, that there is a potential thermal runaway in this zone. Otherwise, the process does not proceed.

The method then checks, in step 150, whether a threshold number Z of potential thermal runaways has been detected in the same zone. Indeed, as explained above, a thermal runaway in one zone of the battery propagates very quickly to the other zones. Therefore, if a number lower than the threshold number Z of potential thermal runaways is detected, it is considered that it is not a real thermal runaway. On the contrary, if several potential thermal runaways are detected at step 150, then it is considered that a thermal runaway is occurring in the battery (step 160). When it has detected the existence of a thermal runaway, the battery management unit transmits the necessary information to the cockpit of the aircraft and/or commands the emergency operations planned in the event of a thermal runaway. .

The method according to Figure 1 is a general method in which all internal components of the battery are treated similarly. In another embodiment, shown in Figure 2, the nature of the components is taken into consideration. For example, data buses are treated separately from sensors such as voltage sensors and temperature sensors. In the example of FIG. 2, where each zone of the battery comprises both voltage sensors and temperature sensors, the method processes in parallel the loss of a voltage sensor (processing 400) and the loss of a temperature sensor (process 300). The method also processes the loss of a data bus in parallel (processing 200) because numerous data pass through the same data bus, and in particular the data from the temperature sensors and the data from the voltage sensors. The loss of a data bus is treated differently from the loss of a sensor because the sensor data passes through the data bus; therefore, if a data bus has a one-time problem (such as a disconnection), this results in no data from both the sensor and the data bus; to avoid "false positive", i.e. to avoid that a specific problem of a data bus is not detected as a thermal runaway, the loss of a data bus is treated differently from the loss of a sensor in the process of figure 2.

The diagram of FIG. 2 shows an example of the method 100 of the invention in the case where each zone of the battery comprises voltage sensors and temperature sensors each connected, by data buses, to the battery management device. Of course, other types of sensors, such as current sensors, could be taken into consideration in the method of the invention, instead of or in addition to voltage and temperature sensors, the processing of the loss of these sensors being identical to the processing 300 and 400 described in connection with Figure 2.

In the example of Figure 2, the method checks in step 410 if a voltage sensor is lost. This step 410 is identical to step 110 of method 100, except that it is applied to the voltage sensors. If a voltage sensor is detected as lost, at step 410, then the method checks (step 420) if this loss occurred during the time window X. Step 420 for the voltage sensor is identical to step 120 of FIG. 1 . If the loss of the voltage sensor occurred earlier than the time window, then the loss of this sensor is not taken into consideration for the detection of a thermal runaway (step 350). On the contrary, if the loss of the voltage sensor occurred during the time window X, then the processing 400 continues with a step 430 of verifying the number of voltage sensors lost in the same zone. If the number of voltage sensors lost in the same zone is greater than the threshold number Y, with Y for example equal to 3, then it is considered that there is a potential thermal runaway in the zone (step 440).

The processing 300 of the loss of a temperature sensor is identical to the processing 400 of the loss of a voltage sensor. Thus, it is checked at step 310 if a temperature sensor is lost (this step 310 is identical to step 110 of method 100, except that it is applied to temperature sensors). If a temperature sensor is detected as lost, at step 310, then the method checks at step 320 if this loss occurred during the time window X. Step 320 for the temperature sensor is identical to step 320. step 120 of FIG. 1 . If the loss of the temperature sensor occurred earlier than the time window, then the loss of this sensor is not taken into consideration for the detection of a thermal runaway (step 350). On the contrary, if the loss of the temperature sensor occurred during the time window, then the processing 300 continues with a step 330 of checking the number of temperature sensors lost in the same zone. If the number of temperature sensors lost in the same zone is greater than the threshold number Y, with Y for example equal to 3, then it is considered that there is a potential thermal runaway in the zone (step 340).

The method then includes a step 360 during which it is checked whether potential thermal runaways have been detected in the same zone, for the voltage sensors and for the temperature sensors. This step 360 corresponds to step 150 of FIG. 1 in the case where the threshold number Y is equal to 2. Indeed, if a thermal runaway occurs in a zone of the battery, then several internal components (voltage sensors , temperature sensors, or others) have been destroyed. In step 360, it is determined whether at least two potential thermal runaways have been detected; if so, then the method proceeds to step 270 described later.

In parallel with processing 300 and 400, the method performs processing 200 for the loss of a data bus. The processing 200 of the loss of a data bus consists, when a data bus is detected as lost at step 210, in checking at step 220 whether this loss occurred during the time window X. step 220 for the data bus is identical to steps 320 and 420 for the loss of a sensor. If the loss of the data bus occurred earlier than the time window X, then the loss of this data bus is not taken into consideration for the detection of a thermal runaway (step 250). Conversely, if the loss of the data bus occurred during the time window X, then it is considered that there is a potential thermal runaway in the area (step 240).

The processing 200 continues with a step 260 of checking the number of data buses lost in the same zone. If two data buses are detected lost in the same area and if it has been determined in step 360 that several potential thermal runaways have been detected in the same area by the processings 300 and 400, then it is considered that a thermal runaway occurs in the battery (step 270). When it has detected the existence of thermal runaway, the battery management unit transmits the necessary information to the cockpit of the aircraft and/or commands the emergency operations planned in the event of thermal runaway.

FIG. 3 represents, in functional form, an example of the function to be integrated into the battery management device, located outside the battery cells. This battery management device can, for example, be a BMS (for Battery Management System, in Anglo-Saxon terms) integrating a unit 10 for determining thermal runaway, comprising for example an electronic processing card. In the exemplary method of FIG. 2, the thermal runaway determination unit 10 receives, as input, the data from the temperature sensors, the data from the voltage sensors and the state of the data buses and provides , at the output, thermal runaway detection information and information on the location of said thermal runaway. In particular, in the example of FIG. 3, the thermal runaway determination unit 10: receives, as input, the data from the temperature sensors 11 of zone 1 of the battery, the data from the voltage sensors 12 of zone 1 and the state of the data buses 13 of zone 1, the data of the temperature sensors 14 of zone 2 of the battery, the data of the voltage sensors 15 of zone 2 and the state of the zone 2 data bus 16; and provides, as output, information 17 for detecting thermal runaway in zone 1 and information 18 for detecting thermal runaway in zone 2.

[0042] Of course, the unit 10 receives the data from all the sensors and data buses whose loss the method wants to detect, regardless of the type of sensors, the type of buses and the zones of the battery, and provides thermal runaway detection information for all the zones of the battery.

[0043] In some embodiments, the thermal runaway detection function can be implemented in a management unit other than the BMS. It can be integrated into any battery processing unit through which the measurements pass (for example an LTC 6804 battery monitor, etc.).

An example of implementation of the thermal runaway detection function according to the invention is shown in Figure 4, in conjunction with Figure 3. The example implementation in FIG. 4 shows, for zone 1 of the battery, the input receiving the data from the temperature sensors 11, that receiving the data from the voltage sensors 12 and that receiving the state of the data 13. FIG. 4 also shows: the processing line 21 for the loss of the temperature sensors 11 (which corresponds to steps 310 to 340 of the method of FIG. 2), the processing line 22 for the loss of the voltage sensors 12 (which corresponds to steps 410 to 440 of the method of FIG. 2), the processing line 23 of the loss of data bus 13 (which corresponds to steps 210 to 260 of the method of FIG. 2), the test 31 of determination of the number of potential thermal runaways of the sensors (which corresponds to step 360 of the method of FIG. 2), and the determination 32 of a thermal runaway in zone 1 (which corresponds to step 270 of the method of Figure 2).

FIG. 5 represents examples of timing diagrams of a simulation of the loss of a temperature sensor (curve A), of a simulation of the loss of a data bus (curve B) and of the resultant of the curves A and B, after applying process 100 (curve C). On curves A and B, the signal goes to 1 when a sensor/bus loss is detected. In the example: just after time t0 (that is to say at to plus a few tenths or hundredths of a second), the signal changes to 1 on curve A: the loss of a first sensor is detected; at time t1, the signal remaining at 1 on curve A signifies that the loss of a second sensor has been detected; the signal of curve C then changes to 1: thermal runaway is detected; at time t2, the signal of curve A goes to 0: the detection of sensor losses (curve A) and the detection of thermal runaway (curve C) are reset; between times t2 and t3, the signal of curve B changes to 1: the loss of a communication bus is detected; at time t3, the signal of curve B remains at 1: the loss of a second communication bus is detected; the signal of curve C then changes to 1: thermal runaway is detected.

The method as just described not only makes it possible to detect thermal runaway using only the components already integrated into the battery, that is to say without the addition of any new component, but it also makes it possible to determine the zone of the thermal runaway. This method is also applicable regardless of the type of battery cells since the only information used is that relating to the loss of data.

[0047] Although described through a certain number of examples, variants and embodiments, the method of detecting a thermal runaway according to the invention, and its implementation device, comprise various variants, modifications and improvements. which will be obvious to those skilled in the art, it being understood that these variants, modifications and improvements fall within the scope of the invention.

Claims

[Claim 1] Method (100) for monitoring the state of health of a battery with explosive cells comprising a plurality of internal components distributed in a plurality of zones (zone 1, zone 2), each zone of the battery comprising at at least one explosive cell, each internal component being associated with a means for checking the consistency of said internal component, the method comprising at least:

- a first data consistency check (110) of a first internal component of a zone of the battery, and

- a second verification (110) of consistency of the data of a second internal component of the same zone of the battery, the first and second verifications being separated by at most a predefined time interval (X), a thermal runaway being detected (160) when first inconsistent data is detected during the first consistency check and second inconsistent data is detected during the second consistency check.

[Claim 2] Process according to claim 1, characterized in that it comprises:

- a plurality of first and second consistency checks (110), each combination of first and second consistency checks being performed for a set of first and second internal components, of different natures; And

- detection (140) of a potential thermal runaway when first and second non-coherent data are detected for a set of first and second internal components.

[Claim 3] Method according to Claims 2, characterized in that it comprises a confirmation (270) of thermal runaway (TR) when at least a first and a second potential thermal runaway (140) are detected, the first runaway thermal potential (340) resulting from non-coherent data of a first set of first and second internal components of a same zone, the second potential thermal runaway (240) resulting from non-coherent data coherent of a second set of first and second internal components of the same zone.

[Claim 4] Method according to any one of Claims 1 to 3, characterized in that the internal components of the battery comprise at least one data sensor positioned inside the cells of the battery and/or at least one data positioned near the battery cells.

[Claim 5] Method according to Claim 4, characterized in that the data sensors comprise voltage sensors and/or temperature sensors.

[Claim 6] Method according to any one of Claims 1 to 5, characterized in that the time interval (X) is of a predefined duration, varying between a few minutes and a few tens of minutes.

[Claim 7] Method according to any one of Claims 1 to 6, characterized in that a zone comprises a cell or a set of several cells of the battery.

[Claim 8] Method according to any one of Claims 1 to 7, characterized in that the number of internal components in the same zone of the battery is a predefined parameter depending on the battery, this number being at least equal to two .

[Claim 9] Device for monitoring the state of health of a battery with explosive cells, characterized in that it comprises a battery management unit, located outside the cells of the battery and implementing the method according to any preceding claim.

[Claim 10] Device according to Claim 9, characterized in that the battery management unit comprises a unit (10) for determining thermal runaway receiving, as input, data relating to the internal components (11 - 16 ) and providing, as output, thermal runaway information and a location of said thermal runaway (17-18).